The present invention relates to magnetic recording media for use, for example, in flexible type magnetic disk storages, magnetic tape storages, magnetic card storages, and rigid type magnetic disk storages, and to magnetic storages.
Investigation and development of magnetic recording media that have, as a recording layer, a thin magnetic layer such as an iron oxide thin film, an iron nitride thin film, and a magnetic metal alloy thin film are under way in order to meet the demand for high density of magnetic recording. These thin film media are in many cases formed on a nonmagnetic substrate by means, for example, of the sputtering process, the vacuum deposition process, the plating process, or the ion plating process, and it can be said that these thin film media are suitable for obtaining high recording density because, for example, the film is thin, and the coercive force and magnetization are high. However, the magnetic recording medium using such a magnetic thin film becomes susceptible to damage due to the slide of the magnetic head, and thus there is a drawback that the durability of such a medium is poor. Since magnetic recording media or the like that are used as magnetic files must have particularly high reliability, it is quite important in order to obtain high density recording.
In prior magnetic recording mediums using a continuous thin film, in order to overcome the above problem, there are proposed, for example, techniques of forming a C type protective film on a magnetic film (Japanese Patent Laid-Open Nos. 54017/1986, and 54019/1986), a technique of forming an organic fluid lubricant additionally on a C type protective film (Japanese Patent Laid-Open No. 96512/1986), a technique of forming a protective film of a carbide or nitride of Si, Zr, Hf, Ti, Ta, Nb, or W (U.S. Pat. No. 32464), and a technique of forming a protective film of a oxide, nitride, carbide, or boride of Zr, Ti, Ta, or Hf (Japanese Patent Laid-Open No. 66722/1988). Further, Japanese Patent Laid-Open No. 4419/1988 discloses the use of a protective film of a carbide of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Si, or B, and Japanese Patent Laid-Open No. 214115/1986 discloses the use of a protective film of Fe-Ni-Cr alloy or the oxide thereof.
The method of forming media generally includes, for example, the sputtering process, the vacuum deposition process, the plating process, and the ion beam sputtering process, and it is known to use, for a magnetic layer, Co-Ni-Zr-N alloy described, for example, in Japanese Patent Laid-Open No. 224121/1986.
However, according to a study performed by the inventors, in the case of using a C type protective film, since, for example, the hardness of the protective film is low, the carbon is liable to be oxidized, and the adhesion of the liquid lubricant is poor, the durability of the magnetic recording medium is not sufficient in the case wherein the thickness of the protective film is made lower to about 60 nm or below. Further in the case wherein the nitride or carbide of Si, Zr, Hf, Ti, Ta, Nb, or W is used for the protective film, or in the case wherein the oxide, nitride, carbide, or boride of Zr, Ti, Ta, or Hf is used for the protective film, in spite of the fact that the hardness of the protective film is high in comparison with C, since the friction coefficient between the magnetic head and the protective film is high, the adhesive strength between the protective film and the magnetic film is low, and the material itself is relatively brittle, there were such problems that abrupt damage such as cracks or peeling was liable to occur to the magnetic recording medium. Furthermore, the sliding endurance at the time when, for example, sudden vibrations were applied to the apparatus, and the corrosion resistance were unsatisfactory.
From another point of view, in the above prior art, since the nonmagnetic protective film is provided separately, there are advantages that the degree of freedom of the selection of the protective material is high, and the sliding endurance reliability can be made very high, however, there is a problem that the space between the magnetic head and the medium is increased due to the thickness of the nonmagnetic protective film, so that high recording density is hardly realized owing to the so-called spacing loss.